The screw sizes refer to the length of the shaft, not the diameter of the head or socket. P5 is the standard pentalobe size for all these screws, regardless of length.

I agree that the notation is a little confusing. I think it's because, with standard sized hardware like for your house, you have shaft diameter (say 1/8" or 3mm) and shaft length (say 3" or 7.5cm). So we're programmed to think of small numbers like that as diameter. But in this case, they're length.

Do you have good Test Point Voltages? It appears there are silver colored Test points on the I/O Board. I am working on a water spill and trying to troubleshoot if both the I/O board and the Logic need replaced.

P5 pentalobe screwdrivers are too big! The correct size for these screws are p4 pentalobe. P5 pentalobe was just able, with difficulty, to turn some of the screws. If the screws were at all tight, my p5 was unable to get them out, and started to strip the screws. A p4 screwdriver fit better and removed the screws with ease. (I was using high quality Wiha brand screwdrivers.)

Very simple installation. The screwdriver heads were exactly what we’re needed, one head for the outside case screws, the other for the screws holding the battery in place. The computer started right up. Now to see how the battery holds up, but I have a good feeling about this!

There is a nub on the inside of the case which is attached to the battery. When you try to pull it open, it appears to be attached to the plastic casing of the battery, which sometimes splits. I gently unhooked the nub from the battery before removing the case fully. This seems to happen if the battery has suffered some drop damage (plastic parts broken around screws and parts of plastic frame split). Just an FYI in case your lower case doesn't pull away easily.